The present invention relates generally to disc drive data storage systems. More particularly, the present invention relates to attenuating the disturbance to the positioning of a read/write head of a first actuator assembly in a dual-actuator disc drive caused by the motion of a second actuator assembly in the drive.
Disc drives read and write information along concentric tracks formed on discs. To locate a particular track on a disc, disc drives typically use embedded servo fields on the disc. These embedded fields are utilized by a servo subsystem to position a head over a particular track. The servo fields are written onto the disc when the disc drive is manufactured and are thereafter simply read by the disc drive to determine position. A servo system samples the position of the read/write head relative to a particular track at a particular sampling rate and adjusts the position of the head.
In a typical servo system, the actual position of the read/write head relative to a given track is sensed and compared to the desired position of the head. A position error signal (PES) indicative of the difference between the actual and desired positions is provided to a servo controller. Based on the value of the position error signal, the servo controller provides a servo control signal to a power amplifier that amplifies the servo control signal and provides it to a voice coil motor. The voice coil motor is coupled to an actuator that moves in response to the application of the amplified control signal to the voice coil motor. An actuator arm that holds the read/write head is coupled to the actuator. In this way, the servo controller controls the positioning of the read/write head relative to a particular track on the disc surface.
Magnetics technology has continued to allow for rapid growth in the areal density of disc drives. With the increase in capacity of magnetic disc storage devices used as the main file for large computer systems, fast data access performance is essential. Along with increasing areal density have come faster access times and faster throughput. Each of these technology improvements requires higher performance servo system and mechanical structures. The rotary dual-actuator structure is effective in meeting the high access performance and faster throughput requirement. Two individual channels and actuators are designed to operate simultaneously. However, the dual-actuator structure tends to suffer from the mechanical interaction between actuators when attaining the required head positioning. The motion of one actuator, especially during track seeking, will generate vibrations which will significantly affect the positioning accuracy of the other actuator while track following.
The present invention provides a solution to these and other problems and offers other advantages over the prior art.
The present invention serves to attenuate the disturbance to the positioning of a read/write head of a first actuator assembly in a dual-actuator disc drive caused by the motion of a second actuator assembly in the drive.
One embodiment of the present invention is directed to a method of attenuating the disturbance to the positioning of a first read/write head, associated with a first actuator assembly, caused by the motion of a second actuator assembly. Pursuant to the method, the servo control signal provided to the second actuator assembly is also provided to an adaptive filter that also receives the position error signal of the first actuator assembly. The adaptive filter then produces a feedforward signal adapted to offset the disturbance to the positioning of the first read/write head caused by motion of the second actuator assembly. The adaptive filter adjusts its parameters based upon the received position error signal and the received servo control signal. The feedforward signal is provided to the servo loop of the first actuator assembly.
Another embodiment of the present invention is directed to a disc drive that includes first and second actuator assemblies, corresponding first and second servo controllers, and an adaptive filter. The first actuator assembly positions a first read/write head relative to a disc surface. The first servo controller receives a first position error signal that is indicative of a difference between the actual position of the first read/write head relative to a disc surface and the desired position of the first read/write head. The first servo controller provides a first servo control signal to the first actuator assembly based on the value of the first position error signal. The second actuator assembly positions a second read/write head relative to a disc surface. The second servo controller receives a second position error signal that is indicative of a difference between the actual position of the second read/write head relative to a disc surface and the desired position of the second read/write head. The second servo controller provides a second servo control signal to the second actuator assembly based on the value of the second position error signal. The adaptive filter receives the second servo control signal and the first position error signal and provides a feedforward signal to the first actuator assembly. The feedforward signal is designed to offset the disturbance to the position of the first read/write head caused by the motion of the second actuator assembly. The adaptive filter adjusts its parameters based upon the second servo control signal and the first position error signal.
These and various other features as well as advantages which characterize the present invention will be apparent upon reading of the following detailed description and review of the associated drawings.